The Elgin, S.C., community has been shaken by over 80 earthquakes since December 2021, and after four months of no tremors, the area has started shaking again. “We weren't expecting anything to come back, and then these two in the last three days have reminded us it’s not over yet," said Daniel Frost, Assistant Professor at the University of South Carolina Department's of Earth, Ocean & Environmental College. After studying the data, Frost and his collaborator, Zhigang Peng, professor in the School of Earth and Atmospheric Sciences, have come up with an idea. “Our theory is they are occurring on a fault of the Eastern Piedmont fault system, which is a known fault system, not an active fault system but known," Frost said. "Any earthquakes happening on these pre-existing faults are just kind of resettling and shuffling, maybe a little of disturbance because something has changed, but it's not the kind of ongoing tectonics like on the West Coast.”